this part that connects to the gutter downspout is a cap of some sort that goes over a receiving part that goes to sewer drains. I'm not sure what it is called. My home was built in the late 1920s. I'm wondering if there is a more modern replacement for this part or a better way to redo and seal this because I think it sometimes backs up during heavy rain and leaks into the basement. You can see it doesn't make a complete seal. Thank you.

Gutter view Cap view

  • 1
    The more modern part provides less seal. The real problem, if it backs up, is that it backs up! The pipe may have collapsed, partially collapsed, been invaded with tree roots etc. While it seems like a major maintenance project it might be time to replace the pipe. You might be able to send a camera down to inspect. Not sure how broad your DIY skills are i.e. the difference between renting equipment for the job or contracting out the repair/replacement.
    – Tyson
    Jun 16, 2018 at 16:45
  • Thanks, I wasn't sure if caps like this were fabricated anymore out of cement like this one. I do need to disassemble the entire thing to see if it is full of debris or if the pipe has collapsed. I guess I'm looking for a better way to seal the cap at the joint once I can clean it all out. Lexel or some other type of silicone?
    – Vincent
    Jun 16, 2018 at 17:36
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    Think about it thugs way: the discharge pipe needs to be able to carry the water away at a rate greater than it arrives. The seal isn’t/shouldn’t be critical, the water needs to be carried away and not back up.
    – Tyson
    Jun 16, 2018 at 17:59

1 Answer 1


You can find adapters like this example: rectangular downspout to circular pipe made out of plastic. Maybe cut the plastic flanges to fit your pipe.
But as commenters have said, seal the connection will only make the water back up the downspout.

downspout adapter

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